76 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 18, No. 1

starch dispersions LLS the amount of iodine is increased to- ward an excess. Under identical conditions of test the waxy starches seem to differ in the color produced by iodine as one proceeds from type to type. Listed in order of decreasing red and increasing violet contents the starch-iodine dispersions may be arranged as fdllows: waxy rice, waxy corn, and waxy barley. To this series may be added in order potato amylopectin and corn amylopectin. This order coincides with the arrangement of Baldwin, Bear, and Rundle (1) who have suggested that i t is also the order of increasing length of chain ends for the respective starch molecules.

M E T H O D

Thirty milligrams of starch are dispersed in 10 ml. of 1 N potassium hydroxide by allowing the mixture to stand with oo- easional shaking a t 0 " C. for 1 to 2 hours. For starch in the whole granule state, 20 ml. of 0.5 N potassium hydroxide are uBed for the dispersion. The dispersion is neutralized with 1 N hydro- chloric acid to a phenolphthalein end paint and 1 drop of acid added in excess. The solution (pH 4 to 6) is then made up to 100-ml. volume, giving a starch concentration of 0.03%. By proceeding in this fashion, a constant amount of salt is introduced into each sample. Large amounts of salt, which produce changes in the iodine color, are to be avoided. To 10 ml. of the solution in a 16- by 150-mm. test tube is added 0.5 ml. (10 drops) of 0.01 N iodine solution (KI = 0.014 M ) dropwise, with shaking. After 0.1 ml. (2 drops) has been added, the color of the solution is ob- served. At this point, the presence of smdl amounts of amylose in amylopectin will be evidenced by a blue color. The remainder of the 0.5 ml. of iodine is then slowly added and the color again observed. Further addition of iodine is unnecessary and in some cases may vitiate the calor t.est by superimposing the color of

'

free iodine on the starch-iodine color. All observations of color are made by transmitted daylight or a daylight fluorescent lamD and

S t I._.. .I_... I _I._. ""1"1, "_. "..~~..""-l~.."..~".~..~l_IY""..""y starches or starch fractions and to be comparable among different laboratories, must be perfomed under uniform conditions in the absence of a large excess of iodine. A procedure is outlined for the rapid determination of starch-iodine colors. I t is especially satisfactory for rapid estimation of the purity of amylaveetin when contaminated with less than 6 to 8% amylose.

LITERATURE CITED

, I \ Qa lAnin D D D Q ""2 D . . - A L D 77 r *- "L- \., l Y . " ....., _". A"., &*. -., A*_ -., * , _,,&. y,w,,&_ Soc.. 66. 111 (1944).

(2) Bates, F. L.. Frenoh, D., and Rundle, R. E., Zbid., 65, 142 (1943). (3) Hanes, C. E., and Cattle, M.. Pmc. Roy. SOC. (London), B125, 387

,101m \L.,yy,. (4) Kerr, R. W., and Trubell. 0. R.. Paper Trade J. , 117, No. 15, 25

(5) McCready, R. M., and Hassid, W. 2.. J . Am. C h m . Soc., 65. 1154 (1943).

r r n n m \'a1*1.

(6) MacMasters. M. M., and Hilbert, G. E., IND. ENG. CHEM., 36,

(7) Munsell, A. E. O., "Munsell Book of Color", Baltimore, Md.,

(8) Ridgeway, Robert, "Color Standards and Color Nomenolaturd',

(9) s

958-63 (1944).

Munsell Color Co.. 1929.

Washington, D. C.. published by the author. 1912.

A Versatile I JOS. W.

U. S. Naval Ordnance Plant, Tt

4rc-SI MACEC le Amorh

park Stand IO wp Corp., Forest Park, Ill.

N arc-spark stand combining the adjustments of the pin- type stand and the versatility of the Petrey stand (1) has

been developed which is capable of supporting heavy weights . . . A

. .

Th, Da.np.~ p'Laye 11 IIIauLLIucu ,,UILI ~i~lr L ~ U L ~ L L L U ~ . UJ Y L L ~ D Y ~ U U

hy two 1.8-cm. (0.5-inch) thick sections of micarta (Figure 1). All screws which fasten the micarta to the sample plate eto., are offset from each other a t least 2.5 cm. (1 inch). By ths means a t least 2.5 em. (1 inchi of air or micart,% insnlst,e t,he mmnle nlat,n ana does not place any Strain on.the Ovtlcal bar or the svectro-

A ~ - - ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ . . ~~~~ ~~~~~~

graph. The &e, shape, and vertical adjustments of thk stand simplify nondestructive spectrographic analyses on relatively massive parts. In many laboratories this stand will broaden

from the remainder of ihe stand. The micarta is fastened to two

the sample plate can easily be e x i t sample as one electrode and a gra The notch must be large enough s

the edge at the sample plate towards the spectrograph slit 8 notch is cut, 2.5 cm. (1 inch) wide and 2.5 em. (1 inch) deep, similar to the cut-out portion of the Petrey stand. The sample lying on

ed from the bottom, using the phite rod as the other ($3, 3). 30 that the excitation will be lite rod and not between the

by trial. I n th;; case, extra &&- in the tap of the plate, in order thr bring the proper notch toward the 5

YlMPLE PLATE

2 S€CT/ONS STEEL of h7CARTA

,Figure 1. Method of lnii

it the plate may be turned to ;pectrograph slit.

dating Sample Plate Figure 9. Arc-Spark Stand

January, 1946 A N A L Y T I C A L E D I T I O N 77

solid pieces of steel which lead to one side of the optical bar, where they are attached to two bars of steel with teeth on the outer side which act as a rack for a rack and pinion motion.

-A commercial-type speed reducer (15 to 1) with a reducer arm extending from each side was purchased and placed on a heavy steel platform about’ 10 cm. (4 inches) above the base of the stand (Figure 2) . h pinion was attached to each reducer arm in such a manner as to contact the rack part of the uprights. On the motor extension part of the speed reducer a micarta knob was attached, to control the vertical motion of the sample plate.

The base, 28.5 cm. (11.25 inches) square and 2.5 cm. (1 inch) thick, rests on the table which supports the spectrograph (Bausch & Lomb large Littrow). Thus, the ent,ire weight of the stand and sample is supported with no strain on the optical bar or the spec- trograph.

A l l parts of the stand are of heavy, sturdy steel, to ensure rigid- ity. Although the stand is heavy (35 to 40 kg.), it is not cumber- some or bulky. I t has supported over 50 kg. (100 pounds) with- out bending or twisting. Wit,h weights of this size, however, a thumb-type setscrew is placed on the side to contact one of the movable uprights. With smaller samples (5 to 10 kg.) this set- screw is not necessary, as the sample plate will remain in the po- sition in which it is placed by the rack and pinion movement.

This stand is so constructed that the cent,er of the notch in the center of the edge of the sample plate towards the spectrograph slit is exactly on the optical axis when the stand is placed firmly against the optical bar (Figure 2). In some instances, where the optical bar is of different design (Hilger, etc.), two slots in the base of the stand are advisable. Bolts can then be placed through these slots and through the supporting table. The stand can then be adjusted until it is properly aligned and the bolts tightened to give the same effect as a t the author’s laboratory, where the weight and position of the stand against the optical bar are used to hold the stand in proper alignment. Once the stand is in po- sition, i t is no longer necessary to move or adjust it., except with the rack and pinion motion.

The base of the stand i R grounded to eliminate slight shocks due to induction from the sample plate, although the stand is usually adjusted by a gage before t,he sample is excited and it is not necessary to touch the stand during excitation.

Small fixtures to hold pins, etc., can easily be made to clip or screw onto the sample plate. Thus, the stand is used for many and varied types of samples, as either an upper or lower electrode holder as desired.

One lead from the source is attached to the sample plate by a countersunk screw, and the other lead to the portion of the regu- lar B. & L. arc-spark stand which is used. The source leads are connected through a switch to convert from arc to spark as neces- sary. The stand is used at all times (with or without fixtures as necessary) as’one pole of the source used.

The stand described has been in use over a year and can be recommended for various sizes, shapes, and tveights of samples, either arc or spark. The direct current arc has been used for over an hour (arcing solutions with a fixture attached to the stand) with less than 1-minute interruptions every 5 minutes, without undue heating of the sample plate or stand.

ACKNOWLEDGMENTS

The author wishes to express his sincere gratitude to the He is particularly obliged to Drafting and Tool Departments.

H. P. Conrad, senior chemist, for his active help.

LITERATURE CITED

(1) Churchill, J. R., IXD. EXQ. CHEW, ANAL. ED., 16, 653 (1944). (2) Guettel, C. L., J. Optical SOC. Am., 34, 141 (1944). (3) Kincaid, H. F., Ib id . , 34, 141 (1944).

Apparatus for Vacuum Distillation of Volat i le High-Melt ing Solids H E N R Y A. GOLDSMITH, Standard Varnish Works, Staten Island, N. Y.

H E vacuum distillation of volatile high-melting solids T necessitates laboratory apparatus of special design. In ordinary apparatus, the distilling solid soon clogs the narrow pass- age between the distilling vessel and the receiving vessel, par- t,icularly in the inaccessible places underneath stoppers and in the interior of the receiving vessel.

The first consists in heating the narrow parts to a temperature above the solidifying point of the distilling solid. Haehn (3) accomplished this by a hot oil jacket, Steinkopf (8) by an electrically heated wire coil. Hauschild (4) used a specially designed still head which could be flamed directly. The second method consists in using specially designed flasks in which inaccessible narrow passages between the still and the receiver are eliminated. The most’ im- portant apparatus of this type is the sword flask designed by Anschuetz (6 ) , or its variat,ions by Baer ( I ) , Muencke (6), and others (5, 7 ) . Another has been described by Bolstad and Dun- bar (@.

However, none of this equipment is readily available or avail- able in sizes large enough to be practical for the handling of fairly large quantities of chemicals. A simple method was de- vised for this purpose, utilizing standard laboratory glassware (Pyrex).

The apparatus consist,s of a large three-necked flask (5 liters), and a retort (0.5 or 1 liter), the neck of which has been cut off conveniently. The shortened neck of the retort is inserted into the center neck of the flask (see figure). The other two necks of the flask hold a thermometer and a capillary tube. The vacuum connection is made through an upward-curved glass tube in- serted into the tubulature of the retort. Heating is best carried out by inserting the flask deep into u suitable bath. Before charging, the flask should be tested for its ability to iTlthstand a vacuum, taking adequate precautions. (Specially hand-picked flasks are available from Corning Glass Works. Caution must be used in all cases.)

Two methods are used to overcome this difficulty.

The vacuum attachment clogged only when too much air was allowed to enter the apparatus through the capillary tube, and drops or particles of the distilland were carried up beyond the receiver. I t was also found helpful to suspend, near the end of a distillation, a large test tube inside the center neck of the flask. This was done by means of a hook of noncorroding wire which was inserted through the neck of the retort and anchored to the sharp edge inside. By suspending the test tube within the center neck of the flask, the path of the distilling vapors is greatly shortened. Otherwise it would be necessary to overheat the con- tents of the flask to force the distillate up to the receiver.

An apparatus like the one described is available in large sizes, is comparatively inexpensive, and has operated satisfactorily in distilling fairly large amounts terruptions.

n

of material with only few in-

LITERATURE CITED Baer, E., ISD. EBG. CHEY.,

Bolstad, L., and Dunbar, R. E.,

Haehn, H., Z. angew. Chem., 19, 1669-70 (1906).

Hauschild, K., Chem. Fabrik , 1937, 375.

Houben, J., “Die Methoden der organischen Chemie”, T’ol. I, 3rd ed. , Leipaig, Georg Thieme, 1925.

Lamar-Cohen, “Xrbe i t smet h- oden fur organisch-chemische Laboratorien”, 5th ed., Vol. I, p. 76, Leipaig, Leopold Voss, 1923.

Morton, A. A,, “Laboratory Technique in Organic Chem- istry”, p. 101, New York, McGraw-Hill Book Co., 1938.

Steinkopf, IT., J. prakt. Chem., 109,347-51 (19%).

ABAL. ED., 16, 399 (1944).

Ib id . , 15, 464 (1943).